1. Field of the Invention
The present invention relates to pattern formation methods and pattern formation apparatuses, exposure methods and exposure apparatuses, and device manufacturing methods, and more particularly to a pattern formation method and a pattern formation apparatus that form a pattern on an object mounted on a movable body, an exposure method and an exposure apparatus that expose an object, and a device manufacturing method that uses the pattern formation method and the exposure method.
2. Description of the Background Art
In a lithography process for manufacturing microdevices (electronic devices) such as semiconductor devices, liquid crystal display devices or the like, an exposure apparatus, which forms a pattern on a substrate that is coated with a resist or the like, for example, a photosensitive object (hereinafter, generally referred to as a wafer) such as a wafer, a glass plate or the like, is used.
Because the semiconductor device or the like is formed by overlaying a plurality of layers of patterns on a wafer, an operation (an alignment) that makes the relative positional relation between a pattern that has been already formed on the wafer and a pattern image optimal is necessary for the exposure apparatus. As a method of the alignment, the EGA (Enhanced Global Alignment) method is mainly used. In the EGA method, the following procedures are employed: (1) a plurality of specific shot areas (which are also called sample shot areas or alignment shot areas) on a wafer are selected in advance; (2) positional information of alignment marks (sample marks) arranged in the sample shot areas are sequentially measured; and (3) a statistical computation by the least-squares method or the like is performed using the measurement result and alignment information in design of the shot areas, and array coordinates of the shot areas on the wafer are obtained. Therefore, in the EGA method, the array coordinate of each shot area can be obtained with high throughput and relatively high accuracy (refer to Kokai (Japanese Unexamined Patent Application Publication) No. 61-044429).
In the alignment described above, alignment marks arranged in a plurality of sample shot areas are measured. Accordingly, a wafer needs to be moved along a route with which a plurality of alignment marks are sequentially positioned within a detection area (a detection field) of a mark detection system (an alignment detection system). Therefore, separately from a movement area of the wafer required for the time when exposure is performed, a movement area of the wafer required for the time when the alignment is performed has to be secured below the mark detection system. In particular, in the case where the exposure position and the alignment system are placed spaced apart, the range in which the movement area for the exposure time and the movement area for the alignment time overlap is narrow, and accordingly the relatively large movement area as a whole of the wafer needs to be secured.
Further, conventionally, a wafer alignment operation (a measurement operation of sample marks) was performed prior to starting exposure of the wafer. Therefore, when the number of sample shot areas increases, the measurement takes a considerable amount of time, which could lead to the reduction in throughput of the entire exposure apparatus. From such a viewpoint, recently, a stage device based on a so-called twin-stage method, which aims at improving the throughput of the entire exposure process by preparing two wafer stages and carrying out the parallel processing in which while performing exposure at one of the wafer stages, alignment is performed at the other of the wafer stages, has been developed and has been employed in the exposure apparatus.
However, in the case of employing the stage device based on a twin-stage method, while one of the wafer stages moves within a two-dimensional plane and exposure is performed, the other of the wafer stages moves within the two-dimensional plane and alignment is performed, and therefore collision between the wafer stages needs to be prevented while both stages are operating.
As a method to realize the prevention, it is considered that a movement area in which one of the stages moves while performing exposure and a movement area in which the other of the stages moves while performing alignment are severally set so that the movement areas do not overlap. Due to this setting, however, the movement area of each stage widens, which could lead to the increase in the footprint and therefore to the increase in size of the apparatus.